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Old 09-19-2012, 09:09 PM
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keitho64 keitho64 is offline
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OK so I am going to resurrect an old thread. My 1969 911 has an electric fuel pump mounted in the engine compartment. It is feeding a pair of weber carbs so I am running the fuel pressure at 4psi and it is controlled by an adjustable regulator. This was the factory installation so it has been this way for a long time, it is pulling the fuel through rather than pushing.

I am running into a situation where the fuel pressure will intermittently drop to 1.5 to 2 psi. When this happens my wide band o2 sensor will show AFR greater than 15.6.

I am going to relocate the fuel pump and mount it at the base of the tank and push the fuel through vs pull, which is how it is operating now. I am not sure if my pump is failing, if it is sucking air or vapor locking.

After reading this thread and a few others the general consensus is electric pumps operate better when pushing. I know my car came from the factory with the electric pump pulling but the modern fuel blends may be playing a part in the problem.

OK so now the real question, should I add a return line for the tank while I am at it? Is a return line needed on a carb setup? I assume not since it never had one but best to check first.

Thanks

Keith
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